[jira] [Updated] (HDDS-14212) S3G stuck on failover to a new leader OM

["Sammi Chen (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDDS-14212?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sammi Chen updated HDDS-14212:
------------------------------
    Fix Version/s: 2.2.0
       Resolution: Fixed
           Status: Resolved  (was: Patch Available)

> S3G stuck on failover to a new leader OM
> ----------------------------------------
>
>                 Key: HDDS-14212
>                 URL: https://issues.apache.org/jira/browse/HDDS-14212
>             Project: Apache Ozone
>          Issue Type: Bug
>          Components: S3, s3gateway
>            Reporter: Aleksei Ieshin
>            Assignee: Aleksei Ieshin
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 2.2.0
>
>
> As per discussion here: [https://github.com/apache/ozone/discussions/9477]
> Our ozone cluster is running with kube; we have a bunch of kube nodes, each node has one S3g and one DN running. Some kube nodes additionally have one OM or one SCM instance running. We have three OMs: om0, om1, and om2.
> So, for some reason, one of the kube nodes with S3g, DN, and *om0* (leader) running went into a non-Ready state for a few minutes (so om1 was still running but didn't serve any traffic). That caused *om2* to take over the leadership. A few seconds later, *om1* returned to the cluster.
> All S3gs failed over to the new OM leader, except one, which stuck in that failover attempts mode. Restarting that failing S3g helped resolve the issues.
> h4. Investigation
> Later, the investigation showed the following:
>  # Cluster had a very low (non-default) setting that made it quickly exhaust its failover limits 
> {code:java}
> "ozone.client.wait.between.retries.millis": "250"
> "ozone.client.failover.max.attempts": "16"
> {code}
> - `hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/protocolPB/GrpcOmTransport.java` line 93: we have `private int failoverCount = 0;` - All threads share this counter; it never resets.
> - Also, in `GrpcOmTransport.shouldRetry`(258) we run `action = retryPolicy.shouldRetry((Exception)ex, 0, failoverCount++, true);` which is also shared between requests.
> - Next in `OMFailoverProxyProviderBase.getRetryPolicy.getRetryAction`, we still use that global `failoverCount` checking ` if (failovers < maxFailovers)`(258), which always returns `return RetryAction.FAIL;`(263) once we reached the `maxFailovers`
> I propose to change the value of *failoverCount* per request, rather than making it a global flag. 
>  



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